Comparison of three intestinal permeability methods

The determination of intestinal permeability remains a challenge. The Ussing chamber is an ex vivo technique which is generally well accepted. However, this technique is tedious and requires a biopsy which can only be obtained through invasive surgery or post-mortem. It also represents a spot sample, sometimes less than 1 cm2. The everted gut sac technique uses a more relevant sample size, and in vivo permeability measurements using Co-EDTA or lactulose are much more practical. Our objective was to compare these 3 techniques. For this, 72 piglets were sampled either 3.5, 7.5, or 10.5 d post weaning. Both lactulose (1.3 g, 9.5 Å) and Co-EDTA (0.6 g, 10.0 Å) dissolved in 15 g demineralized water were administered intragastrically. Two hours later a blood sample was obtained through venipuncture. Subsequently, a 15 cm segment harvested at 25, 50, and 75% of the length of the small intestine was inverted, filled with phosphate buffered saline (PBS) containing 5 mM glucose, and sealed. Sacs were inserted for 60 min. in an aluminum foil covered bath with aerated PBS containing 125 µM FITC-dextran (14.0 Å) and maintained at 39°C after which both the sac content and medium were analyzed for FITC. Statistical analysis was performed using the Pearson correlation test of SPSS 19 (2010). The FITC analysis of the buffer revealed that the FITC concentrations dropped quickly (half-life ± 3 h), even though it was kept from contact with light by aluminum foil. This is raising doubts about the validity of the test. Serum concentrations of Co-EDTA and lactulose were positively correlated (r = 0.67, P <0.01). FITC dextran, corrected for a predicted change in half-life of stock solution, in contrast, did not correlate with either lactulose or Co-EDTA, for any of the segments compared. In conclusion, a correlation was found between Co-EDTA and lactulose suggesting that both marker molecules measure the same change in permeability, while ex vivo determinations using FITCdextran in everted gut sacs requires additional work before it can be applied.